Craniotomy Closures

ABSTRACT

Craniotomy closures comprising surgical fasteners are described for use in reattaching a skull flap removed from the skull of a patient during brain surgery. Methods of using the same are also described. Surgical strips used in combination with the fasteners are shaped to follow the perimeter contour of the skull flap. The craniotomy closures are designed to encourage bone growth and healing of the skull flap and they can be used to deliver medication and bone growth enhancement materials to the surgical site.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of Ser. No. 11/333,102 filedJan. 17, 2006.

FIELD OF THE INVENTION

The invention relates to surgical fasteners, particularly for use inreattaching a skull flap removed during brain surgery and methods ofreattaching the skull flap using the fasteners. In further aspects, theinvention relates to a surgical strip used in combination with thefasteners, methods of implanting the fasteners and strips of theinvention and methods which enhance bone growth and the consequenthealing of the skull flap and the skull.

BACKGROUND OF THE INVENTION

Surgical access to the brain for neurosurgical procedures is created byremoving a portion of the patient's skull to provide an exposed area ofsoft tissue of the brain for surgery, a procedure termed a craniotomy.The craniotomy is determined by the location of the pathology within thebrain, the safest/easiest access route and the degree of exposurerequired for the procedure. Once the location is determined, the firststep is to create an initial perforation of the full thickness of theskull. Special skull perforators are available to create perfectly roundholes but most surgeons simply use a rounded, end-cutting burr to createthe perforation. Typically the perforation is in the range of about11-15 millimeters (mm) in diameter. A surgeon may choose to create morethan one perforation around the perimeter of the planned craniotomy.Some surgeons prefer a single perforation and others use more than one,but there is no standard number. Once this hole is created, it allowsthe insertion of a rotary powered surgical instrument (e.g., acraniotome) which is used to create a continuous cut (also called anosteotomy cut or a kerf) around the perimeter of the craniotomy. Thiskerf begins and ends at the perforation when there is one perforation orit runs from one perforation to another when more than one perforationis made in the skull. The kerf is made with a side cutting burr which isshielded from the dura (outer covering of the brain) by a foot plate onthe craniotome. The foot plate extends below and forward of the cuttingburr and the surgeon keeps the tip of the foot plate in contact with theinner surface of the skull as he performs the craniotomy. The typicalkerf is made freehand with an approximately 2 mm diameter burr. Theshape of the craniotomy is therefore highly variable and the kerf is notalways oriented perpendicular to the skull. The kerf may be larger than2 mm in some areas as well. Over the course of the kerf, the skullthickness will vary, typically over the range of 3-8 mm in adults.

Once the cut is complete, the skull flap is removed from the skull andplaced on the sterile back table for reinsertion at the end of theprocedure. After completion of the soft tissue surgery (typically 1-6hours), the skull flap is inserted back into the craniotomy and fixatedto prevent movement and restore the original contour of the skull. Thesurgeon may bias the skull flap toward one side or another to createbone-to-bone contact in a particular area or he may leave a gap aroundthe entire flap. The scalp is then closed and the patient is sent to theneurosurgical intensive care unit for recovery.

If complications develop while the patient is in the hospital, there maybe the need for emergency access to the brain through the craniotomysite. In addition, some patients may return for subsequent craniotomiesin the same region, particularly in cases of recurrent tumors.Postoperative imaging studies (MRI or CT) are generally conducted on allpatients. There is no clear evidence that the skull flap ever completelyheals (solid bony union) in adults. It is more likely that a combinationof new bone formation and fibrous connective tissue fills the gapbetween the skull and the skull flap.

From a surgeon's perspective, the method of reattaching the bone flapmust be safe, simple to use, be rapidly applied, permit emergentre-entry, not interfere with postoperative imaging studies, providestable fixation and have an acceptably low profile. The ideal methodwould result in complete fusion of the bone flap to the native skullwith no long term evidence of prior surgery.

Current methods of reattaching the skull flap include drilling a seriesof small holes in the edge of the skull and the edge of the flap.Sutures are then passed through the corresponding holes and the flap issecured back into the skull opening from which it was taken. Because thefit is not exact due to the material removed by the craniotome, the flapcan sag and sit slightly below the surface of the skull resulting in adepressed area that is obvious through the skin.

Another common reattachment method substitutes stainless steel wire forthe suture material and fewer holes are used. There is still the risk ofa cosmetically objectionable depressed area resulting. Metallic cranialfixation is (generally) only ever removed if it becomes symptomatic orif it interferes with subsequent surgeries.

More recently, surgeons have begun to use the titanium micro plates andscrews that were developed for internal fixation of facial and fingerbones. While this method results in a more stable and cosmetic result,it is relatively expensive, does not insure fusion and leaves foreignbodies at the surgical site.

All of these methods take ten minutes to one hour of additional surgeryafter the soft tissue (brain) surgery.

There is another method in which a titanium rivet (or clamp) is placedinside the skull with the stem of the rivet (clamp) passing between theskull and the flap. A large “pop rivet” type tool is used to force anupper titanium button down over the stem of the rivet, locking the flapand the skull in place between the upper and lower buttons. Three orfour of these rivets and buttons are used to secure the flap in place.This method can be faster than other methods and less expensive than thetitanium plates, but more expensive than sutures or wires. Just as withtitanium plates and screws, fusion is not assured and foreign bodiesremain in the patient.

According to the present invention we have developed new surgicalfasteners for, and methods of, reattaching a skull flap in a skullopening. The fixation provided utilizing a fastener of the invention andpracticing the methods of the invention is secure and cosmeticallyacceptable. The fastener is used in combination with materials which canenhance bone growth in a manner which causes healing by means ofbone-to-bone reattachment of the skull flap to the skull.

The term “perimeter contour” as used herein with reference to the skullflap means “the shape of the outer boundary around the skull flap.”

The term “shaped to follow the perimeter contour” means “formed aroundthe perimeter contour.”

SUMMARY OF THE INVENTION

The surgical fasteners of the present invention allow the surgeon toreattach the skull flap in generally the same position from which it wasremoved, thereby maintaining the contour of the skull in a manner whichis cosmetically desirable. The fasteners also position the flap in theskull in a manner which provides a generally even gap (the kerf) betweenthe flap and the skull around the perimeter of the flap. Flexiblesurgical strips used in combination with the surgical fasteners can beshaped to follow the perimeter contour of the skull flap and,consequently, the contour of the opening in the skull from which theflap was removed. These strips are placed or implanted in the kerfbetween the flap and the skull. In a preferred embodiment, a craniotomyclosure of the invention is comprised of at least two fasteners, used toreattach the skull flap, and one or more than one surgical strip.

The fastener comprises a flange which is disposed over and adjacent tothe skull flap and the skull. A projection extends from the underside ofthe flange. The projection extends into the kerf and acts as a spacerbetween the skull flap and the skull to make the generally even gap. Insome embodiments, the projection can be flexible and somewhat wider thanthe kerf to make a snug fit. But the flexibility of the projectionshould be somewhat limited so that the function of the projection to actas a spacer is not compromised.

A strip or ribbon of material can comprise the element of the surgicalstrip which is shaped to follow the perimeter contour of the skull flap.Some embodiments of the surgical strip are provided with one or morecavities disposed along its length. The cavities generally are locatedin the strip so that they are disposed between the skull flap and theskull when the strip is implanted in a patient. For example, the cavitymay have a uniform cross section along the entire length of the stripsuch as in the shape of a U, V, J, W or pleats or corrugations or it maybe a closed tube or a solid having the cross-sectional shape of acircle, oval, ellipse, square, rectangle, triangle or any other closedgeometric shape.

The strip can also be a moldable material which may be, for example, inthe form of a putty, paste or gel (i.e., a putty-like, paste-like orgel-like material) or a compressible material or any other material thatis formable and which is rolled before it is implanted by insertion intothe kerf or which is implanted by pressing, pouring, squeezing orinjecting the material into the kerf and the material then takes itsshape as a strip following implantation.

The outer width of the cross-section of a strip is sometimes referred toherein as the outer width of the channel. References to such stripshapes herein each refer to the shape of a cross-section takentransverse to the length of the strip. In other embodiments one or moretubular elements are used to make the strip and these are disposedbetween the skull flap and the skull when the strip is implanted in apatient.

The surgical strips have side portions which are disposed between theskull flap and the skull when the strip is implanted. These sideportions can optionally have openings such as holes, slits or lateralslots which permit bone regrowth. Additionally the slits may be orientedalong a transverse axis through one sidewall and a portion of the bottomsection of the strip, allowing the strip additional flexibility. Thestrips also can have a bottom portion. The tubular and solid shapedelements have bottom and top portions and these bottom and/or topportions also can have openings such as holes or lateral slots.

As a further option the cavities or tubular elements can be filled orpartially filled with medication, bone paste, bone growth enhancers andthe like. The putty-like, paste-like, gel-like or compressible materialreferred to herein also can be comprised of or impregnated withmedication, bone paste, bone growth enhancers and the like.

Other variations and embodiments are described in more detail below andin the drawings and further variations will be apparent to those skilledin the art based upon the principles of the invention set forth herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings are not intended to illustrate every embodiment ofthe invention but they are representative of embodiments within theprinciples of the invention. The drawings are for illustrative purposesand are not drawn to scale.

FIG. 1 is a representative view of a human skull showing one possiblelocation and configuration of a craniotomy skull flap.

FIGS. 1A and 1B are section views of portions of skull bone and cranialcavity.

FIG. 2 is a perspective view of a fastener of the invention having aV-shaped projection extending from the bottom of a flange. Theprojection has an aperture therethrough. FIG. 2A is a top view of thefastener and FIG. 2B is a section view. FIG. 2C illustrates a fastenerwith a solid V-shaped projection. FIG. 2D is a perspective view of theFIG. 2 fastener having a strip threaded through the aperture thereof andFIG. 2E is a section view of FIG. 2D.

FIGS. 3, 3A, 3B and 3C are top views illustrating various shapes of theflange portion of the same type of fastener as illustrated in FIG. 2.

FIG. 4 is a perspective view of a fastener of the invention having a “W”shaped projection extending from the bottom of the flange.

FIG. 5 is a perspective view of a fastener of the invention having aY-shaped flange and two V-shaped projections.

FIG. 6 is a perspective view of the underside of a fastener of theinvention having an X-shaped flange and two V-shaped projections whereineach projection is connected on one side and the connections are onopposite sides of an opening in the flange.

FIG. 7 is a perspective view of a fastener of the invention having aY-shaped flange and two projections from the underside.

FIG. 8 is a perspective view of a fastener of the invention having asevered V-shaped projection.

FIG. 9 is a perspective view of a fastener of the invention having amodified conical projection.

FIG. 10 illustrates a craniotome having a cutting diameter of generallythe same width as the projection of a fastener.

FIG. 11 is a perspective view of a skull flap having three fastenerspositioned thereon for affixation thereto.

FIG. 12 illustrates a skull flap reattached to a skull using thefasteners of the invention which have been installed with screws.

FIG. 13 is a section view of a skull flap reattached to a skullincluding a section of a fastener of the invention.

FIG. 14 illustrates in section a conventional craniotome cut to remove askull flap from a skull.

FIG. 14A illustrates in section a more angled cut (sometimes referred toherein as a “pumpkin cut”) to remove a skull flap from a skull.

FIG. 15 is a perspective view of a woven strip with leaders to threadthe strip through apertures in the projections of the fasteners of theinvention.

FIG. 16 illustrates a rolled strip of a putty-like, paste-like, gel-likeor compressible material which can be used as a strip of the invention.

FIG. 17 is a section view illustrating the relationship of the strip ofFIG. 16 to the skull flap and the skull.

FIG. 17A is a section view illustrating the relationship to the skullflap and the skull of a strip 161 which has been pressed into the kerfand formed in situ. And FIG. 17B illustrates the use of a U-shaped stripas a “floor” for strip 161.

FIG. 18 is a perspective view of an embodiment of a strip of theinvention comprising a perforated, U-shaped, flexible strip and FIG. 18Ais a section view of the FIG. 18 embodiment.

FIG. 19 is a perspective view of an embodiment of a strip of theinvention comprising a V-shaped flexible strip and FIG. 19A is a sectionview of the FIG. 19 embodiment.

FIG. 19B is a perspective view of the FIG. 19 embodiment which isstraight rather than pre-curved.

FIG. 20 is a perspective view of an embodiment of a strip of theinvention comprising a W-shaped flexible strip and FIG. 20A is a sectionview of the FIG. 20 embodiment.

FIG. 21 is a perspective view of a strip of the invention having aflexible strip comprised of three stacked tubes and FIG. 21A is asection view of the FIG. 21 embodiment.

FIGS. 21B and 21C are perspective views of flexible tubular strips whichalso can be filled or solid. In FIG. 21C the tubular strip has a helicalslit along its length.

FIG. 22 is a perspective view of fasteners of the invention incombination with a perforated, J-shaped, flexible strip. FIG. 22A is atop view and FIG. 22B is a section view of the FIG. 22 embodiment.

FIG. 23 is a perspective view of a fastener of the invention which canbe used in conjunction with various strips. FIG. 23A is a bottom viewand FIGS. 23B and C are section views of the FIG. 23 fastener. FIGS. 23Dand 23E are top views of the FIG. 23 fastener, each illustrating thefastener with a different strip threaded through the aperture.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For reference, a human skull 1 with a craniotomy skull flap 2 (alsoreferred to herein as a flap) is shown in FIG. 1. The skull flap 2 isdefined by a burr hole 3 and the connecting osteotomy cut or kerf 4,wherein the skull portion of the burr hole is designated in FIG. 1 as 3a and the skull flap as 3 b. The skull flap 2 has a perimeter contour 5but it need not be of the particular shape shown and may have any numberof burr holes 3. On the opposing sides of the osteotomy cut 4 is therespective bone edge surface 6 of the skull flap 2 and the surroundingbone 7 of the skull 1, respectively. The bone edge surface 6 has aperimeter contour 5 matching the contour of the surrounding bone 7 ofskull 1.

The skull 1 and skull flap 2 are either made from bone that has a threelayer composition, as shown in FIG. 1A, or a single layer as shown inFIG. 1B. Referring to FIG. 1A, the outermost layer is the outer corticalbone 8 and the innermost layer is the inner cortical bone 9. Betweenthese two stiff layers is a relatively soft middle layer of cancellousbone known as the diploe 10. Interior to the inner cortical bone 9 isthe cranial cavity 11 housing the brain 12 and its surrounding duramatter 13. FIG. 1B illustrates the condition wherein the skull bone iscomprised entirely of cortical bone 14.

The present invention is particularly adapted for securing a craniotomyskull flap 2 to the skull 1, but may be used in other situations whereappropriate. The present illustrative discussion assumes that a surgicalstrip of the invention is being used in combination with a fastener ofthe invention to close a craniotomy skull flap 2 having one burr hole 3but the same principles apply if the surgeon makes more than one burrhole in order to open up the skull for surgery. The kerf 4 may be normalto the surface of the skull 1 or at an angle thereto. As we shallexplain in more detail below, angled cuts are presently preferredwherein the angle is such that the top of the skull flap 2 is largerrelative the bottom than it would be if a cut normal to the surface ofthe skull was made. This is sometimes referred to herein as a “pumpkincut” because the cut is similar to one made when cutting the top of apumpkin to make a jack-o-lantern.

The term “surgical strip” is used herein to mean a surgical strip whichis used in combination with a fastener of the invention.

The surgical strips of the invention, also referred to herein as strips,can be made straight or with a precurvature to reduce kinking when theyare shaped to follow the perimeter contour of the skull flap.

The strips also can be made from a moldable material that has, forexample, a putty-like, paste-like or gel-like consistency or acompressible material or any other material that is formable into ashape that will fit in the kerf. Strips of this type may be pressed,poured, squeezed or injected into a kerf and formed in situ. Forexample, a strip can comprise a paste-like or putty-like materialcontaining bone, either allograft or autogenous bone, and/or other bonegrowth enhancing material.

Combinations of two or more than two strips of the invention can beused. Numerous variations are possible when such combinations are usedas will be apparent to those skilled in the art based on the disclosuresherein. For example, one strip may contain bone particulate and/orgrowth enhancers and another may contain antibiotics or othermedications. Alternatively, one strip may be used as a floor for anotherstrip. For example, a U, V. W or J-shaped strip or mesh or tubular stripmay be threaded through or affixed to the projections of the fastenersto create a floor for a putty-like, paste-like, gel-like or compressiblestrip.

The fasteners and the surgical strips of the invention can be made ofvarious biocompatible materials and combinations of biocompatiblematerials. Suitable materials include biocompatible metals, alloys,plastics and reinforced plastics which are commonly used in surgicalimplants of all kinds. Such materials include materials that havesufficient strength and flexibility to meet the objectives of theinvention. The materials also can optionally be porous, semi-porous,semi-permeable or maleable. Many of the materials that have beenapproved by the United States Food and Drug Administration (FDA) forsurgical implant applications are also suitable. Some examples ofsuitable materials include DuraGen® dural graft matrix, available fromIntegra Lifesciences Corporation, 311 Enterprise Drive, Plainsboro, N.J.08536, USA and Gelfoam® sterile compressed sponge, a product of Pfizerdistributed by Pharmacia & Upjohn Company, Division of Pfizer Inc., NewYork, N.Y. 10017.

Generally speaking, there are three main types of alloys used inbiocompatible metals today, titanium alloys, cobalt alloys and stainlesssteel alloys. An exhaustive list is available on the FDA website whichalso provides the reference numbers and effective dates of the ASTM orISO standards for many of the materials that are suitable. Some examplesinclude unalloyed titanium and titanium alloyed with aluminum, niobiumand/or vanadium; stainless steel and other irons alloyed withmolybdenum, chromium, cobalt, tungsten, aluminum, nickel, manganese orvanadium in various combinations, various other stainless steels andother iron alloys, for example, with aluminum oxides, zirconium oxides,tantalum and calcium phosphates. This list is not intended to beexhaustive.

Numerous types of high strength polymers also are employed to makeimplants and many of these are identified not only on the FDA websitementioned above but also on the ASTM website. Examples of suitable highstrength polymers include polyetheretherketone (PEEK), epoxys,polyurethanes, polyesters, polyethylenes, vinyl chlorides, polysulfones,polytetrafluoro-ethylene (PTFE), polycarbonates, polyaryletherketone(PAEK), polyoxymethylene, nylon, carbon fiber polyester,polyetherketoneetherketoneketone (PEKEKK), silicones, hydrogels and thelike. When a polymer is used, a small wire or other radiopaque materialcan be incorporated in the main body of the base for purposes of x-raydetection.

The foregoing lists of materials may have application in someembodiments of the present invention but not in others as will beapparent to those skilled in the art based on requirements of strength,flexibility, machinability and the like for the particular application.The lists are intended to be illustrative and not exhaustive. Othermaterials and new materials may be employed based upon the principles ofthe invention as set forth herein.

For purposes of this specification, the term “high strength polymer(s)”is defined as any biocompatible non-bioabsorbable polymer, copolymer,polymer mixture, plastic or polymer alloy having sufficient strength towithstand without failure the stresses that a fastener of the inventionwould normally be subjected to during surgery or in the body.

Bioabsorbable material can also be used to make all or a portion of oneor more of the component parts of the fasteners or strips of theinvention and/or the bioabsorbable material can be applied as a partialor complete coating on such component parts. Some component parts can bemade from different materials than others as will be apparent to thosehaving skill in the art based upon the disclosures herein.

The term “bioabsorbable material” as used herein includes materialswhich are partially or completely bioabsorbable in the body.

Suitable bioabsorbable materials include DuraGen, Gelfoam, collagen,polyglycolide, poly(lactic acid), copolymers of lactic acid and glycolicacid, poly-L-lactide, poly-L-lactate; crystalline plastics such as thosedisclosed in U.S. Pat. No. 6,632,503 which is incorporated herein byreference; bioabsorbable polymers, copolymers or polymer alloys that areself-reinforced and contain ceramic particles or reinforcement fiberssuch as those described in U.S. Pat. No. 6,406,498 which is incorporatedherein by reference; bioresorbable polymers and blends thereof such asdescribed in U.S. Pat. No. 6,583,232 which is incorporated herein byreference; copolymers of polyethylene glycol and polybutyleneterephthalate, and the like. The foregoing list is not intended to beexhaustive. Other bioabsorbable materials can be used based upon theprinciples of the invention as set forth herein. Some of the mostcommon:

Poly-L-lactic acid (PLLA) Poly-DL-lactic acid (PDLLA) Polyglycolic acid(PGA) Polydioxanone (PDS) Polyorthoester (POE) Poly-C-capralactone (PCL)

Bioactive materials can be admixed with the bioabsorbable materials,impregnated in the bioabsorbable materials and/or coated on the outersurface thereof. Bioactive materials, including natural and/or syntheticmaterials, also can be used to fill cavities in the fasteners and thesurgical strips. These materials can include, for example, bioactiveceramic particles, bone chips or paste, platelet rich plasma (PRP),polymer chips, synthetic bone cement, autologous materials, allograft,cadaveric materials, xenograft, nanoparticles, nanoemulsions and othermaterials employing nanotechnology, capsules or reinforcement fibers.And they can contain, for example, antimicrobial fatty acids and relatedcoating materials such as those described in Published U.S. PatentApplication No. 2004/0153125 A1; antibiotics and antibacterialcompositions; immunostimulating agents; tissue or bone growth enhancersand other active ingredients and pharmaceutical materials known in theart.

The products of the invention which are made with bioabsorbable materialcan be made by molding, extrusion, heat shrinking or coating thebioabsorbable material on a base which has been provided with attachmentmeans such as those described in our pending patent application Ser. No.11/025,213 filed Dec. 29, 2004 which is incorporated herein byreference. Some of the screws and other fastening devices described inour pending patent application Ser. No. 11/025,213 filed Dec. 29, 2004can also be used in or in combination with the surgical strips andfasteners of the present invention. When the bioabsorbable material willhave functional mechanical properties which are not made from the basematerial, the bioabsorbable material can be molded onto the base in thedesired shape. Alternatively, the bioabsorbable material also can becoated, shrink wrapped or molded onto the base. If necessary, thebioabsorbable material can be machined to the desired shape and/ordimensions.

As will be apparent to those skilled in the art, the sizes of thesurgical strips and fasteners of the invention can be varied to meettheir intended applications. The shapes can take various forms inaddition to those illustrated without deviating from the principles ofthe invention. And the sizes, lengths and widths can be varied forparticular applications within the principles of the invention set forthherein.

Various methods can be used to employ the surgical strips and fastenersof the invention as will be apparent to those skilled in the art basedupon the embodiment(s) of the surgical strips and fasteners selected foruse by the practitioner. For example, the fastener may be attached tothe skull flap first, then the skull flap would be positioned in theskull opening and the fastener would then be attached to the skull. In apreferred embodiment, the fasteners are made from a material that allowsthe flange to be intraoperatively bent so that the fastener andreattached flap will follow the original contour of the skull. Theflange can be bent, for example, before it is affixed to the skull flapor after it is affixed to the skull flap, but normally it isautomatically bent by the pressure imparted by the fasteners (screws,tacks, other means) when it is affixed to the skull. This could befollowed by affixing one or more cranial plugs in the burr hole or holesas needed as described in our copending parent application Ser. No.11/333,102 filed Jan. 17, 2006, the disclosure of which is incorporatedherein by reference. In most embodiments, antibiotics, bone growthenhancers or other materials disclosed herein could be added in cavitiesin the surgical strips and/or fasteners before or after the skull flapis reattached to the skull, as will be apparent to those having ordinaryskill in the art. It should be noted that the terms “affixing”,“affixed” or “affix” as used herein include “snap-fit” and “press-fit”as well as the other means such as screws, staples, tacks, adhesives andthe like as described herein. Other methods will be apparent to thosehaving skill in the art depending upon the characteristics of the skulland/or skull flap, the type of surgery involved and the likelihood orunlikelihood of the need to re-open the surgical site.

As noted above, the surgical strips of the invention can be formedaround the perimeter contour of the skull flap and attached to the skullflap or the strips can be attached to the fasteners before or after thefasteners are attached to the skull flap and before attachment of theflap to the skull. Alternatively, the fasteners can be attached to theskull flap and then the skull followed by insertion of a strip orstrips. The step of attaching the fasteners to the skull flap, andoptionally bending the flanges to conform with the skull contour, can bedone by operating room personnel while the surgeon is performingsurgery. This saves substantial time when the skull flap is reattachedfollowing surgery. The previously attached fasteners support the skullflap and insure that the top of the flap coincides with the top surfaceof the skull. As noted above, the shape of the skull flap is highlyvariable and when it is reattached to the skull it is positioned in amanner to match the position from which it was removed, similar toreplacing a piece of a jigsaw puzzle.

There are numerous suitable options for fastening the fasteners of theinvention to the skull flap and the skull. These include screws,staples, tacks, glues, adhesives, peel off adhesives, press-fit,snap-fit and combinations of two or more thereof. For example, afastener may be stapled onto the skull flap and then press-fit into theopening in the skull. These fastening methods may be used to affix thefasteners to any contacting surface of either the skull flap or skull.

FIG. 2 is a perspective view of a fastener 20 of the invention. FIG. 2Ais a top view and FIG. 2B is a section view. A continuous elongateflange 21 has lower surfaces 28 which overlay both sides of the kerfwhen the fastener is affixed to the skull and skull flap. Optional holes22 can be provided for screws or other devices for affixing the fastenerto the skull and skull flap. A V-shaped projection 23 extends from theunderside of the flange. The projection 23 has an aperture 26 having acentral axis a-a disposed in parallel with lower surfaces 28 and asurgical strip 27 can be threaded through the aperture as illustrated inFIG. 2D and the section view thereof, FIG. 2E. Optional opening 24provides access to aperture 26 after fastener 20 is installed in apatient. The opening 24 opens from the upper surface of the flange 21into the aperture 26 and can be used to assist in threading a strip orstrips through the aperture and/or to insert medication, bone growthenhancers and the like into the fastener.

FIG. 2C illustrates an alternative embodiment of the fastener whereinthe projection 25 is solid and does not have an aperture or an optionalopening through the flange.

FIGS. 3, 3A, 3B and 3C are top views of fasteners of the inventionhaving flanges of various shapes. Flange 32 is T-shaped, flange 34 isY-shaped, flange 36 is L-shaped and flange 38 is X-shaped. Other shapescan be used without departing from the invention.

The projections from the undersides of the flanges can also have variousshapes without departing from the invention and there can be one or morethan one projection from the underside of a flange. FIG. 4 illustrates afastener having projections 43 which make up a W-shape extending fromelongate flange 41. FIG. 5 illustrates a fastener having Y-shaped flange51 having V-shaped projections 53 and 54 extending from the undersidethereof. Apertures 56 in the projections are coaxial. An X-shaped flange61 is provided in the fastener of FIG. 6. One leg of projection 63 isconnected to the underside of the flange on one side of opening 65 andone leg of projection 64 is connected to the underside of the flange onthe opposite side of opening 65. The unconnected legs of the projectionsallow for enhanced flexibility. The fastener illustrated in FIG. 7 iscomprised of a Y-shaped flange 71 and projections 73 and 74. Flange 81of the fastener illustrated in FIG. 8 has projections 83 and 84 whichtogether form the shape of a V which has been severed at point 85. Amodified conical or bullet-shaped projection 93 extends from the bottomof flange 91 in the fastener of FIG. 9. Projection 93 can be solid orhollow.

In the prior art, flat plates were typically used to reattach a skullflap to a skull. The plates did not have projections as describedherein. By sizing the projection so that its width corresponds to thediameter of the cutting burr of a craniotome cutter, and consequentiallythe width of the kerf around the skull flap, the projection centers theflap and allows the surgeon to place the flap in the position itoccupied before it was cut out of the skull. The projection also acts asa buttress to resist inward displacement of the flap and can serve tointraoperatively bend the flange of the fastener or assist the manualbending of the flange to match the contour of the skull. Because theskull flap is cut out in a single pass with the craniotome, theresulting gap (the kerf) between the native skull and flap necessarilycorresponds to the width (diameter) of the cutting burr. To replace theflap in its original position, the surgeon needs to maintain thisuniform gap around the periphery of the flap as he/she applies the rigidfixation using the fasteners. By matching the width of the projection onthe fastener to the diameter of the cutter, this is automaticallyaccomplished.

FIG. 10 illustrates a craniotome 101 with a footplate 103 and a cuttingburr 102 having relatively the same diameter D as the width W ofprojection 23 from fastener 20.

In a preferred surgical method, the fasteners 20 are affixed to theskull flap 2 before the skull flap is reattached to the skull. This isillustrated in FIG. 11 wherein one side of each projection 23 is buttedup against and in contact with the perimeter of the flap, the side beingapproximately tangential to the edge of the flap at the point ofcontact. The number of fasteners employed is at the discretion of thesurgeon. We recommend using at least two and preferably three fastenersor more to insure proper placement of the flap into its originalposition.

When the flap 2 is replaced in the skull 1, the fasteners 20 insure aneven gap (i.e., the kerf 4) around the periphery thereby returning theflap to its original position as illustrated in FIG. 12. Screws 29 areused to affix the fasteners 20 to the skull flap and skull in theillustration but it is understood that other devices or adhesives can beused to affix the fastener as previously described herein.

FIG. 13 is a section view of a portion of FIG. 12 illustrating therelationship of the fastener 20 to the skull flap 2 and skull 1 afterthe skull flap has been reattached to the skull. The projection 23 fitssnugly between the sidewalls of the kerf 4 and the central axis a-a ofaperture 26 is approximately in parallel with the side walls at thepoints of contact of the projection with the sidewalls. Stated anotherway, the central axis a-a of the aperture is approximately in parallelwith the perimeter (or a tangent t-t to the perimeter) at the point ofcontact of the projection with the surface of the perimeter.

Restoration of the original flap position provides the optimum cosmeticresult and the consistent peripheral gap (the kerf) allows for theinsertion of a uniform volume of material all around the flap. Thisinserted material comprises one or more strips of the invention. Forexample, the material could be autologous bone graft as described above,autogenous bone mixed with blood and/or saline, a filler material suchas collagen, DuraGen, Gelfoam or the like, or a combination of bonegraft material and filler. These materials act as strips whether or notthey are supported by the fasteners.

When cutting the flap, the surgeon will keep the craniotome angledperpendicular (normal) to the curvature of the skull or more likely,he/she will deliberately tilt the cutter to produce an angled cutthrough the skull to make a pumpkin cut as described above. This isillustrated in FIGS. 14 and 14A wherein the cut in FIG. 14 is normal tothe skull and the cut in FIG. 14A is a pumpkin cut.

Both methods produce a flap that is widest at its outer or top surfaceand tapers to a smaller dimension across its inner or bottom surface.The corresponding sidewalls of the kerf 4 are generally in parallel.While neither flap would fall freely through the corresponding hole inthe skull, allowing the bone flap to move or settle inwardly would causethe inner surface of the flap to impinge on the brain and wouldsecondarily result in a cosmetically unacceptable depression of thepatient's scalp. Rigid fixation of the flap to the skull solves thisproblem. Prior art metallic plates without a projection span the gapbetween flap and skull and are generally affixed with screws anchoredinto the bone. But the projection beneath the flange of the fastener ofthe invention adds an additional element of strength. It does so withoutadding any additional material to the surface of the skull which wouldincrease the chance that the fixation system of the invention would bepalpable to the patient.

The fastener has a top flange that functions much like a standard boneplate but the addition of the projection beneath the flange fills thegap created by the osteotomy cut (kerf) and acts as a buttress tofurther resist any downward force on the flap. Because the width of thisprojection is matched to the craniotome cutting burr, the lateral wallsof the projection are either in contact with or in very close proximityto the parallel sidewalls of the flap and skull as shown in FIG. 13. Anyinwardly directed force on the flap must now overcome not only theresistance of the flange (in bending) and screws or other anchoringdevices but also must crush the projection which fills the gap.

Because the width (or diameter) of the projection on the fastenermatches the diameter of the craniotome cutting burr, the projectioneffectively restores the removed bone volume at each fastener location.This allows it to function as a three-dimensional spacer, automaticallyrestoring the flap location side-to-side as well as re-establishing thecorrect depth of the flap relative to the skull as shown here.

There is one other advantage attributable to the underside projection onthe fastener. The difficulty of bending plastic plates (without heatingand softening) can be overcome with the fastener design. When the flapwith attached fastener is reinserted into the skull opening, theprojection will be pushed slightly toward the side of the flap. This inturn will bend the flange of the fastener slightly downwardly. Becausethe projection is trapped in the gap between the flap and the skull,this bend is maintained. The surgeon simply pushes the flap down(inward) and the non-secured end of the flange bends to meet the skull.The surgeon then fastens this side in place with the appropriateaffixation device or adhesive. This feature allows a fastener to be madewith a flange that is only slightly precurved knowing that it willself-bend when the flap is inserted into the skull opening. Because theprojection provides added support, this flange can be made more flexiblethan a traditional plate to enhance this property.

FIG. 15 illustrates a mesh strip 150 having a curved leader 152 affixedto one end thereof. An optional leader 154 affixed to the other end isalso illustrated. The leader or leaders can be pre-curved, straight orintraoperatively curved. This embodiment can be used when the strip isto be threaded through the apertures 26 in the fasteners. The leader isused in a similar manner to a needle when sewing with a needle andthread. Any of the strips of the invention that are sufficientlyflexible can be combined with a leader in this manner.

FIG. 16 illustrates a strip 160 made from a putty-like or gel-likematerial. This can be made in the form of a rolled material asillustrated or it can be hand rolled or compressed and pressed into thekerf after the skull flap is reattached to the skull (illustrated asstrip 161 in FIGS. 17A and 17B). Alternatively, this type of fillermaterial can simply be pressed, poured or injected into the kerf afterreattachment of the flap, effectively creating a strip of material insitu in the kerf extending from one fastener to another. As noted above,the objectives of all of the strips of the invention are to close theopenings in the skull and optionally to enhance bone regrowth, providemedication and the like.

The strips also can serve to provide a “floor” to the kerf. Thisprevents filler strips (implanted following implantation of the strip orstrips which provide a floor) such as autologous bone which are pressedinto the kerf, from migrating into the cranium. Furthermore, the stripswhich serve to provide a floor replace some of the volume of the boneremoved with the craniotome so that collected bone from the craniotomewill be adequate to fill the volume remaining in the kerf.

The strips of the invention can be made from various materials and invarious shapes. They can be affixed to the skull flap before it isreattached to the skull, they can be affixed to the fasteners before orafter they are affixed to the skull or they can be implanted afterreattachment. Some of them can be threaded through apertures in thefasteners, others can be affixed to or implanted adjacent to thesidewall of the skull flap and others can simply be inserted adjacentthe fasteners and in attachment with or in contact with the fasteners orwithout necessarily being attached to or in contact with the fasteners.

FIG. 17 is a section view of strip 160 implanted between a skull flap 2and a skull 1. In FIGS. 17A and 17B the strip 161 is comprised of aputty-like, paste-like, gel-like or compressible material which ispressed into the kerf 4 to form a strip in situ. FIG. 17B illustrates anembodiment employing a U-shaped strip 170 which is used as a “floor” forthe strip 161 so that the material of strip 161 (or any other materialor strip in the place of strip 161) will not impinge upon the dura ormigrate into the cranium. Of course various other strips of theinvention can be used as a floor or as a filler to provide medication,enhanced bone regrowth, etc. as will be apparent to those having skillin the art based on the disclosures herein.

FIGS. 18 and 18A illustrate a strip 170 having a U-shape which ispre-curved and sufficiently flexible to be shaped to follow theperimeter contour of a skull flap. Multiple holes 171 are disposedaround the inside perimeter 172 and the outside perimeter 173 ofU-shaped strip 170. The holes 171 permit bone growth for bone to bonereattachment of the skull to the skull flap or they can be used to affixthe sidewalls of the strip to the edges of the skull flap. Bone growthcan be enhanced by filling the U-shaped strip 170 with known bone growthenhancers and/or other bioactive materials as described above. This canbe done before and/or after the strip 170 is implanted in the patient.This concept can be adapted by those skilled in the art to strips ofother cross sections disclosed herein.

FIGS. 19 and 19A illustrate a strip 180 comprised of a V-shaped stripwhich is pre-curved and sufficiently flexible to be shaped to follow theperimeter contour of a skull flap. Multiple slots serve the samefunction as the holes 171 described in respect of the FIG. 18 embodimentand the V-shaped strip 180 can be filled with known bone growthenhancers and/or other bioactive materials and/or medications asdescribed above. FIG. 19B is a perspective view of the FIG. 19embodiment which has not been pre-curved.

The strip 190 illustrated in FIG. 20 is comprised of a W-shaped stripwhich is pre-curved and sufficiently flexible to be shaped to follow theperimeter contour of a skull flap. Slots 191 or holes (not shown) canoptionally be provided through the W-shaped strip to serve the samefunctions as described above.

Strip 200 illustrated in FIG. 21 is comprised of one or more flexibletubes 201 (three illustrated) which are pre-curved and sufficientlyflexible to be shaped to follow the perimeter contour of a skull flap.The terms “tubular” or “tube” as they are used herein are not meant torestrict the lateral cross-section of the tube to only a circularprofile. Oval, elliptical, rectangular or other closed geometric shapedtubular structures (not shown) are also within the meaning of “tubular”or “tube” and can be used with this design. A tube of the invention canbe hollow, filled or solid. Multiple slits 202 or holes or slots (notshown) can optionally be provided in the tubes 201 as with many of theother embodiments discussed above. The slits 202 are narrow cuts madethrough the tubes 201. The tubes 201 also can be filled with known bonegrowth enhancers and/or other bioactive materials as described above.These tubular strips may be packaged (sterile) with the bioactivematerials already filling the cavities. This is also possible for theother configurations but obviously much more practical for a tubularprofile.

As discussed above in respect of the tubular strip of FIG. 21, the tubesof FIGS. 21 B and 21 C can have various cross sections. In FIG. 21 B,tube 203 of strip 204 can be made from a solid, porous, semi-porous,semi-permeable or woven material and/or it can have holes or slots orslits.

Strip 205 in FIG. 21C is comprised of a tube 206 having a helical slit207 which runs the entire length of the tube.

Multiple tubes of the kind illustrated and described in respect of FIGS.21 B and 21 C can be arranged together. For example, they can be stackedas in FIG. 21 or arranged in rows or combinations of rows and stacks orthe like. Combinations of tubes 203 and 206 can also be used in suchmultiple tube embodiments. Tubes may also be made in a rolled form andbone growth enhancers and/or medications can be incorporated into therolled tubular strip. These rolled strips may be sufficiently flexible(or soft) such that they readily conform to the size and shape of thekerf when inserted in a patient's skull.

The strip 220 illustrated in FIGS. 22, 22A and 22B is comprised of aJ-shaped flexible strip 221 which is pre-curved and sufficientlyflexible to be shaped to follow the perimeter contour of a skull flap.This embodiment has been illustrated with fastener 230 which is a slightvariant of the fastener 20 as explained in the below discussion of FIG.23. In this embodiment, the projection 233 purposely positions theJ-shaped cavity of the strip 221 below the level of the underside of theflange 231 to insure that the J-shaped flexible strip 221 remains belowthe top surface of the skull and skull flap. In this embodiment thestrip can be affixed to the skull flap before or after the fasteners areaffixed to the flap or the strip can be affixed to the fasteners beforethe fasteners are affixed to the flap. Any strip having an open upperportion such as a U, V. W or J-shaped strip can be used with a fastenerhaving a compatibly shaped projection.

FIG. 23 illustrates a perspective view of a fastener 230 with acontinuous elongate flange 231 creating lower surfaces 238 each of whichwill be affixed to one side of the kerf when the fastener is implantedin a patient. Optional fastener holes 232 are shown in the flange. AV-shaped projection 233 having an aperture 236 projects from theunderside 234 of the flange and the aperture is illustrated with acompatibly shaped flexible strip 180. In other words, the strip 180 isthreaded through the aperture 236 in the V-shaped projection 233 offastener 230. FIG. 23A is a view of the underside of FIG. 23, FIG. 23Bis a section view taken through the section line 23B-23B of FIG. 23A andFIG. 23C is a section view taken through section line 23C-23C of FIG.23A. FIG. 23D is a top view of a fastener 230 with a V-shaped strip 180threaded through the aperture thereof. Of course, strips of many othershapes could be threaded through the aperture as long as they can bepulled through the aperture. A flexible strip such as, for example, awoven strip or a flexible tube can be threaded through the aperture evenif the cross-section is wider than the aperture. In that case, it willsimply be squeezed within the aperture but allowed to expand to itsoriginal size on both sides of the aperture. This is illustrated in FIG.23E wherein a woven strip 150 has been threaded through the aperture ofthe fastener and the strip 150 is wider than the aperture.

Optional tabs 235 on the inside of the aperture 236 position the strip180 at a distance below the underside of the flange 234. The fastenerscould be affixed to the strip or could be able to slide along itslength. Obviously other strip cross-sections (U, J, W, tubular) could beused in a similar manner.

1. A craniotomy closure comprised of a fastener used to reattach a skullflap removed from a skull during brain surgery, the skull flap having aperimeter contour, the fastener comprising a flange which can bedisposed over and affixed to the skull flap and the skull and aprojection extending downwardly from a lower surface of the flange, theprojection being positioned and sized to fit in a kerf between the skullflap and the skull, and a surgical strip which can be formed around theperimeter contour and which is sized to fit in the kerf.
 2. The closureof claim 1 comprising at least two fasteners.
 3. The closure of claim 1comprising at least two surgical strips.
 4. The closure of claim 1wherein the surgical strip is affixed to the projection.
 5. The closureof claim 1 wherein the projection has an aperture and the surgical stripis threaded through the aperture.
 6. The closure of claim 1 wherein thesurgical strip has a cross-section in the shape of a V, U, J, W or atube.
 7. The closure of claim 5 wherein the aperture is shaped to fitthe surgical strip.
 8. The closure of claim 1 wherein the projection isflexible and is sized to fit under compression in the kerf.
 9. Theclosure of claim 1 wherein the surgical strip is a formable material, amoldable material or a compressible material.
 10. A fastener used toreattach a skull flap removed from a skull during brain surgerycomprising a flange which can be disposed over and affixed to the skullflap and the skull and a projection extending downwardly from a lowersurface of the flange, the projection being positioned and sized to fitin a kerf between the skull flap and the skull when the fastener isimplanted in a patient.
 11. The fastener of claim 10 wherein the skullflap has a perimeter and the projection has a laterally disposedaperture, the aperture having a central axis disposed in parallel withthe lower surface and approximately in parallel with the perimeter at apoint of contact of the projection with the perimeter when the fasteneris implanted in a patient.
 12. The fastener of claim 10 wherein theprojection is flexible and is sized to fit under compression in thekerf.
 13. The fastener of claim 11 further comprising an openingextending from the upper surface of the flange into the aperture. 14.The fastener of claim 10 comprising at least two projections, theprojections being positioned and sized to fit in the kerf when thefastener is implanted in a patient.
 15. The fastener of claim 14comprising more than two projections.
 16. The closure of claim 1 whereinthe surgical strip further comprises a leader affixed to one endthereof.
 17. The closure of claim 1 wherein the surgical strip furthercomprises a leader affixed to both ends thereof.
 18. A method ofreattaching to a skull a skull flap removed from a skull to make anopening in the skull during brain surgery, the skull flap having aperimeter contour, comprising the sequential steps of affixing to theskull flap at least one flange which can be disposed over and affixed tothe skull flap and the skull, the flange having a projection extendingdownwardly from a lower surface thereof, the projection being positionedand sized to fit in a kerf between the skull flap and the skull, shapingat least one surgical strip to follow the perimeter contour of the skullflap and affixing the surgical strip to the skull flap and/or theprojection, and affixing the flange to the skull, thereby affixing theskull flap to the skull.
 19. The method of claim 18 wherein theprojection has a laterally disposed aperture, the aperture having acentral axis disposed in parallel with a lower surface of the flange andapproximately in parallel with the perimeter contour at a point ofcontact of the projection with the perimeter contour, at least onesurgical strip being threaded through the aperture.
 20. A method ofreattaching to a skull a skull flap removed from a skull to make anopening in the skull during brain surgery, the skull flap having aperimeter contour, comprising the sequential steps of affixing to theskull flap at least one flange which can be disposed over and affixed tothe skull flap and the skull, the flange having a projection extendingdownwardly from a lower surface thereof, the projection being positionedand sized to fit in a kerf between the skull flap and the skull,affixing the flange to the skull, thereby affixing the skull flap to theskull, and implanting at least one surgical strip in a kerf between theskull flap and the skull.
 21. The method of claim 20 wherein theprojection has a laterally disposed aperture, the aperture having acentral axis disposed in parallel with a lower surface of the flange andapproximately in parallel with the perimeter contour at a point ofcontact of the projection with the perimeter contour, at least onesurgical strip being threaded through the aperture.
 22. The method ofclaim 20 wherein at least one surgical strip is implanted by pressing,pouring, squeezing or injecting it into the kerf.